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In drm_crtc_helper_set_config, we call drm_crtc_helper_set_mode which may return early and do no operation if the crtc is to be disabled. In this case we merrily swap to the new fb, discarding the old_fb believing that it has been cleaned up. However, due to the early return, the old_fb was not presented to the backend for correct reaping, and nor was the new one - which is about to be reaped via the drm_helper_disable_unused_functions(), leading to incorrect refcounting of the pinned objects. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=27722 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=29857 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=29230 Tested-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
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* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
************************************************************
The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html